In U.S. Pat. No. 4,377,616 there is described a biaxially oriented opaque film having excellent overall characteristics. To use this material for some commercial wrapping purposes, it is necessary that the film be further modified so as to permit printing thereon and to permit the heat sealing or adhesive sealing of the film to itself or other surfaces. In order to prepare the surfaces of polymeric films for ink receptivity or the adhesion of glues and adhesives, it is a common practice to treat the surface of the film to enhance the wettability of these materials. Common techniques employed to increase the wettability of such materials, such as, polypropylene, include corona discharge treatment and flame treatment. In the case of the subject films, however, it has been found that such treatment leads to destructive film-to-film blocking.
It is an object of the present invention to modify films of this type so that in spite of treatment to enhance the wettability of a film surface, the films still will not destructively block together.